Attractive Forces



m1,m2: mass of two objects; r: distance between two objects; G: gravitational constant





Gravitational Force



M: Earth mass, m: mass of object, R: Earth radius, h: object’s height





Gravitational Acceleration



At a height h above the normal surface of the earth



Near the sea level




Force Of Gravity



Force of gravity on earth, a special case of Gravitational force


Newton's First Law



F: forces acting on the object , v: velocity of the object, a: acceleration of the object

Newton's Second Law



m: object’s mass(kg)

Newton's Third Law



Linear Elasticity-Hooke's Law



K: spring constant (n/m), x: displacement(m)

A Mass suspended by a spring

Force Of friction



µ: coefficient of friction, N: normal force

            Fms = µN
                = µPcosα
                = µmgcosα